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3 January 1995 Development of a submicrometer optical chemical sensor
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The near-field interaction between an optical aperture of sub-micrometer diameter and a sample surface can be exploited to spectroscopically probe a biological medium with a resolution unattainable with traditional far-field techniques. A simple, low-cost technique is described for producing a chemical sensor which is based on the principles of near-field optics, and preliminary results obtained using this device to measure pH are reported. Singlemode optical fibers are drawn into sub-micrometer optical fiber tips and then coated with aluminum, to form a subwavelength aperture. By using laser illumination through this aperture, samples can be studied with a resolution better than the wavelength of light. Sub- micrometer pH sensors have been prepared by incorporating the pH sensitive dye fluorescein into a silica based sol-gel glass which is then coated in the form of a thin film onto the fiber tip surface. These sensors were used to monitor the pH of buffer solutions inside micron-size holes in a polycarbonate membrane, and to probe the intracellular environment of mouse embryonic fibroblast cells. It was found that the pH response is reversible in the range 3 - 10. In addition the design potential of the sol-gel process for optimization of the sensor by careful control of the coating thickness is demonstrated.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Scott McCulloch and Deepak G. Uttamchandani "Development of a submicrometer optical chemical sensor", Proc. SPIE 2631, Medical and Fiber Optic Sensors and Delivery Systems, (3 January 1995);


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